Method and apparatus for cleaving optical fiber

ABSTRACT

An optical fiber cleaving tool is disclosed wherein a housing insertably receives an optical fiber extending from a fiber optic ferrule. A cleaving module is contained in a housing for scoring the fiber. A fiber pulling element grasps the fiber at a location spaced from the second location, and simultaneously axially offsets the fiber and pulls the second location away from the first location to effect severing of the fiber at the scored location.

FIELD OF INVENTION

This invention relates generally to a method and apparatus for cleavingan optical fiber and more particularly relates to a method and apparatusfor breaking a scored optical fiber at the scored location.

BACKGROUND OF THE INVENTION

Throughout the development of fiber optic data transmission, it has beenknown that in order to maximize transmission capabilities of the fiberoptic system at locations such as taps and splices, it is essential thatjoined fibers be properly aligned to reduce transmission losstherebetween. It is also known that proper preparation of the end faceof the fiber which is to be connected will reduce transmission lossthrough that fiber end face. It is highly desirable to prepare a opticalfiber end face to have a smooth mirror-type finish thereby providing agreater optical transmission area across the end face. In additiion, itis also desirable to provide a fiber end face which is nearlyperpendicular to the longitudinal axis of the fiber.

There are many known fiber optic cleaving tools which attempt to providethis nearly perfect flat perpendicular end face. Most of these toolsemploy a scoring blade which is brought down into contact with the fiberto score or nick the fiber surface. This causes a weak point in thefiber at which the fiber can be separated by applying proper axialtension to the fiber on each side of the scored location. Placing axialtension on one side of the scored location assure a better cleavedsurface.

Fiber optic termination tools of this type may take many forms. Asdisclosed in U.S. Pat. No. 4,229,876, issued Oct. 28, 1980, an opticalfiber breaker is disclosed where the fiber is placed in axial tensionprior to scoring or nicking the fiber surface. This technique claims toprovide a superior fiber end face. However, U.S. Pat. Nos. 4,202,475,issued May 13, 1980 and 4,322,025, issued Mar. 30, 1982, discloseoptical fiber cutting tools which score a non-tensioned optical fiberand then provide axial tension on each side of the scored location toeffect a cleave. These patents also suggest that this sequence providesa superior optical end face. It is also known to effect severing of thescored fiber by applying axial tension in the form of longitudinalpulling of the fiber on each side of the scored location. A device ofthis type may be seen in U.S. Pat. No. 4,372,048, issued Feb. 8, 1983,and assigned to the assignee of the present invention.

More recently, development of optical fiber cleaving tools has reached apoint where a device is available which both longitudinally pulls andbends the fiber about a scored location to effect the severing thereof.U.S. Pat. No. 4,552,290 assigned to the assignee of the presentinvention, discloses a tool wherein, in sequence, the fiber is firstscored, then axially offset to effect bending, then longitudinallypulled to effect severing. While a tool of this construction provides afiber termination end having an end face of desired qualities, thesequential steps of the tools's operation may prove to be slightlycumbersome in field applications. Thus, it is desirable to provide atool which will provide a suitable termination end face by properlyapplying techniques of scoring and axially tensioning the fiber, yetwill be simple to use and operate in field applications.

A further dichotomy is found in existing optical fiber cleaving tools inthat many tools cleave a bare fiber extending from an optical cable andothers are constructed to cleave a fiber terminated in an opticalconnector or ferrule. The later type tool is obviously more advantageousfor field applications. Examples of the non-connectorized fiber toolsare shown in the above-identified '475 and '025 patents, while theabove-identified '876 patent is representative of connectorized fibercleaving tools. While it is desirable to provide a tool whichaccommodates connectorized fibers, problems associated withconnectorization must be overcome.

A major problem found in tools of this nature, is the ability to cleavethe fiber within close proximity to the egressing end of the fiberferrule. It is even more important to provide a cleaved fiber end facewhich is at a prescribed constant distance from the end of the egressingend of the ferrule. Variations in the length of the fiber with respectto ferrule end, may be caused by improper insertion of the connectorinto the cleaving tool or deformation of the ferrule, itself, due toover insertion of the connector into the cleaving tool. It is desirableto provide a fiber optic cleaving tool which will accommodate a fiber ina fiber optic connector and which will align the connector in the toolto provide a constant predetermined fiber termination length overrepeated uses.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an optical fibercleaving device for cleaving an optical fiber along the length thereof.

It is a more particular object of the present invention to provide amethod an apparatus for breaking an optical fiber at a scored locationto provide a suitable termination end face.

In the efficient of the foregoing and other objects a method andapparatus is provided herein, wherein an optical fiber is supported inan optical fiber cleaving tool. An actuatable cleaving means is movablysupported in the housing adjacent the fiber to score the fiber at alocation therealong. The fiber breaking means engages the fiber distallyof the scored location to place axial tension at the scored location tobreak the fiber thereat.

In a more particular embodiment described herein, the housingaccommodates an optical fiber in an optical fiber ferrule with a portionof the fiber extending therethrough. Actuatable cleaving means issupported on the housing adjacent the fiber ferrule for scoring thefiber. Actuatable fiber breaking means grasps the fiber and axiallybends and pulls the fiber to effect a break at the scored location.Actuation means is provided for actuating both the cleaving means andthe fiber breaking means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an optical cable terminated in an optical fiber connectorassembly.

FIG. 2 shows, in perspective view, the optical fiber cleaving tool ofthe present invention.

FIG. 3 is a partial showing of the cleaving tool of FIG. 2 with theconnectorized fiber inserted therein.

FIG. 4 is a top view of the optical fiber cleaving tool of FIGS. 2 and 3with the cover removed to show the internal workings of the cleavingmechanism.

FIGS. 5a through 5d, shown in schematic fashion, the operation of thecleaving tool of the present invention.

FIGS. 6a through 6d, show in schematic fashion, the further operation ofthe cleaving tool of the present invention which effects severing of theoptical fiber.

FIG. 7 is a diagrammatic representation of the vector forces applicable,in principle, to the tool of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown a fiber optic cable 10 terminated ina connector assembly 12. Cable 10 is conventional fiber optic cableincluding an optically transmissive fiber 14 extending from a plasticjacket 16. The cable 10 is prepared in a suitable manner by cutting backthe plastic jacket 16 to expose an extended length of fiber 14. Theconnector assembly 12 includes a main connector body 18, a rear cableaccommodating sleeve 20 and an extending fiber egressing ferrule 22.Connector body 18 may include at the end thereof, adjacent ferrule 22,screw threads for screw accommodation with another optical device suchas a mating optical connector. Ferrule 22, shown in FIG. 1, may be ofthe type shown and describd in U.S. patent application Ser. No. 527,438,filed Aug. 29, 1983, now abandoned.

Referring to FIGS. 2 and 3, optical fiber cleaving tool 30 is shown.Cleaving tool 30 has an elongate substantially rectangular handle 32 andan upper operable housing 34. The tool 30 also includes an actuatablelever 36 supported on housing 34 for manual operation of the cleavingtool by an installer as will be described in further detail hereinbelow.

Housing 34 includes a transverse, upwardly opening slot 38 whichprovides for vertically insertable accommodation of optical fiber 14supported in connector 20. Adjacent one end of slot 38, housing 34includes an externally threaded, extending sleeve 39 which provides fora screw reception of connector 20. As will be described in furtherdetail hereinbelow, progressive screw attachment of connector 20 tosleeve 39 provides for a progressive axial movement of the connector 20and cable 10 along the longitudinal extent of slot 38. A mountingsurface 35 supports threaded sleeve 39. In preferred form, housing 34includes a plastic, removable cover 34a which provides access to theinternal mechanism of the cleaving tool 30 housed in housing 34. Handle32, which is also removably supported to housing 34, is formed in thepreferred embodiment of a suitably rigid metal.

Referring to FIG. 4, the mechanism of the optical cleaving tool 30 maybe described. Housing 34, of tool 30, supports therein a fiber cleavingmodule 40. Cleaving module 40 includes a support member 42 which formsthe base of cleaving module 40. A perpendicularly extending arm 44extends from support member 42 and supports a cleaving element assembly46. Cleaving element assembly 46 includes a cleaving element 48 formoveable disposition over fiber 14. Cleaving element 48 is supported onarm 44 by a pair of parallel cantilevered spring beams 49a and 49b whichprovide for moveable engagement of cleaving element 48 with fiber 14. Aflex bar 50 is supported over cantilevered 49a and 49b to provide forspring movement of the parallel cantilevered beams 49a and 49b. Theoperation of the cleaving element assembly 46, shown in FIG. 4, issubstantially similar to that shown and described in U.S. Pat. No.4,503,744, issued Mar. 12, 1985, entitled "Cleaving Device For OpticalFibers" and assigned to the assignee of the present invention.

However, it is noted that in the '744 patent, the cleaving elementextends from its support in a direction transverse to the extendingelongate fiber. In the present invention the cleaving element issupported in a direction substantially parellel to the elongate fiber(i.e. cantilevered beams 49a and 49b extend parallel to fiber 14). Thispositioning provides for a more accurate and precise cleaving locationalong the fiber as the cleaving element 48 is fixedly positioned withrespect to fiber 14. No movement of the cleaving element 48 is possiblein a direction parallel to fiber 14. Thus, any inadvertent movement ofthe cleaving element 48 due to shock or other vibration causing amovement of beams 49a and 49 will not change the longitudinal positionof the cleaving element 48 with respect to fiber 14.

Disposed in contact with flex bar 50, cleaving module 40 supports anoperable, retractable, plunger-type mechanism 52 which provides cleavingmovement to cleaving element assembly 46. Plunger mechanism 52 includesa mechanism housing 54 which provides for such retractable of a pair ofaxially aligned rods 56 and 58. A first moveable rod 56 is supported atone end of mechanism housing 54 and is progressively insertable intomechanism hosuing 54 upon movement of lever 36 as will be described indetail hereinbelow. Progressive movement of first rod 56 into mechanismhousing 54 causes corresponding outward movement of second rod 58 whichmoves into contact with flex bar 50 of cleaving element assembly 46,initiating the cleaving action by deflecting flex bar 50 and therebycantilevered beams 49a and 49b. Further progressive movement of firstrod 56 causes further movement of second rod 58 to indirectly causecleaving element 48 to score or nick fiber 14. Plunger mechanism 52includes a retractable feature which upon still further insertion offirst rod 56 will cause second rod 58 to immediatley retract. Thus,continuing linear movement of first rod 56 will not be directly impartedto second rod 58. Accordingly, retraction of second rod 58 will releasethe deflected flex bar 50 and cantilevered beams 49a and 49b andcleaving element assembly 46 will retract from its scoring position aswill be described in detail hereinbelow.

The position of plunger mechanism 52 is vertically adjustable withinhousing 34. This adjustment allows for adjustment in the amount of forceat which fiber 14 is cleaved. As an example the closer plunger mechanism52 is to support 42, the more deflection of cantilevered beams 48a and49b will take place. Thus, more force will be placed on fiber 14 bycleaving element 48.

Cleaving module 40 is supported in housing 34 against the bias of spring60. Spring 60 provides for spring bias movement of cleaving module 40 ina direction parallel to the longitudinal axis of fiber 14. Uponlongitudinal movement of connector 20 occasioned by screw attachment ofconnector 20 to sleeve 39 (FIGS. 2 and 3) the end face 22a of ferrule 20will engage an integral formed stop surface 42a of support surface 42.Continued screw insertion of connector 20 into housing 34 will causemovement of cleaving module 40 against the bias of spring 60. Sincecleaving element 48 is fixedly positioned with respect to support member42 cleaving element 48 will always cleave fiber 14 at a location whichis a fixed distance with respect to stop surface 42a and thus at a fixedposition with respect to ferrule end face 22a. As long as connector 12is inserted to the position where ferrule end face 22a abutts stopsurface 42a, fiber 14 will always be scored at a location predeterminedand fixed with respect to the end face 20a of ferrule 20. Adverseeffects of over insertion are prevented by the spring bias movement ofcleaving module 14. As may be the case with a fixed cleaving module,damage to the ferrule due to over insertion of the connector is avoided.A pair of mating stop members in the form of the outside wall ofmounting plate 35 and the front face of connector body 18 limit axialmovement of connector 20.

Housing 34 further supports at a location spaced from cleaving module40, fiber breaking means 70. Fiber breaking means includes a pair offiber pulling elements 72 and 74. Each fiber pulling element is formedof an elongate spring element which is bent in the configuration shownin FIG. 4. Fiber pulling elements 72 and 74 are preferably made of aspring steel material. First fiber pulling element 72 is a stationarymember fixedly positioned at one end to housing 34. Stationary fiberpulling element 72 includes a fixed base 72a, a cantilevered extendingportion 72b and a depending fiber support 72c. Second fiber pullingelement 74 is configured identical to stationary fiber pulling element72 and is positioned in facing relation thereto. Each extending fibersupport portions, 72c of pulling element 72 and 74c of pulling pullingelement 74, includes a fiber engagement pad 73a and 73b respectively forengagement with fiber 14. Engagement pads 73a and 73b are formed of asuitably resilient material for clamping and securing a portion of fiber14 spaced from ferrule 20. Moveable fiber pulling element 74 issupported along support portion 74a by a support bar 76. Support bar 76is in turn engagable with lever 36 to move in a vertical direction, asshown in FIG. 4, toward stationary pulling element 72. A guide element77 accommodates support bar 76 for sliding receipt therein. Guideelement 77 prevents any rocking Motion of movable pulling element 74. Aswill be described in further detail hereinbelow, upon actuation of lever36 moveable fiber pulling element 74 will move toward and engagestationary fiber pulling element 72 to clamp a portion of fiber 14thereinbetween to effect breaking of the fiber at the scored locatedadjacent ferrule 20.

Having described the elements of tool 30 of the present invention, itsoperation may be described by referring to the schematic drawings ofFIGS. 5, 6 and 7.

Referring to FIG. 5a, housing 34 is shown supporting cleaving module 40in contact with spring 60. Housing 34 also supports stationary pullingelement 72. Lever 36 which is movably supported to housing 34 supportsmoveable pulling element 74 and is positioned for engagement withplunger mechanism 52 for operating cleaving element assembly 46 asdescribed hereinabove. Longitudinal axis 14a is representative of theaxis along which fiber 14 will lie in tool 30.

A. OPERATION OF THE SPRING LOADED CLEAVING MODULE 40

As seen in FIG. 5a, cleaving module 40 is shown positioned adjacentmounting plate 35 of housing 34. Spring 60 urges cleaving module 40 intothis position.

Moving to FIG. 5b, ferrule 22 with fiber 14 extending therefrom isinserted into housing 34 through an opening 35a in mounting plate 35.Upon insertion, front face 22a of ferrule 22 engages stop surface 42a ofsupport member 42. Further insertion of ferrule 22 occasioned by thescrew attachment of connector 12 to mounting plate, as above described,will move the cleaving module 40 against the bias of spring 60 away fromplate 35. As cleaving element 48 is fixed with respect to support member42 the cleaving element 48 will be positioned above fiber 14 at alocation fixed with respect to front face 22a of ferrule 22. Regardlessof the amount of insertion of ferrule 22 into housing 34 this relativeposition of cleaving element 48 with respect to front face 22a offerrule 22 will be maintained. It is noted here that the preciselocation at which cleaving element 48 strikes fiber 14 is predeterminedby the construction of and positioning of element 48 with respect tosupport member 42. It is also noted that with precise construction,fiber 14 may be cleaved spaced from, directly at or slightly inwardly offront face 22a of ferrule 22. However, as shown in the embodimentillustrated herein, fiber 14 is cleaved just inwardly of front face 22aof ferrule 22. The technique for cleaving the fiber inwardly of frontface 22a is shown and described in the above mentioned U.S. patentapplication Ser. No. 462,571. Movably positioning cleaving module 40 inhousing 34 assures the precise repeatable cleaving location of fiber 14.Also, movement of cleaving module 40 prevents damage to ferrule 22 uponinsertion into housing 34 and against stop surface 42a of support member42.

B. SCORING OF OPTICAL FIBER 14

Referring again to FIG. 5b, fiber 14 is shown in position to be cleavedby cleaving element 48. Lever 36 is actuated by manual installeroperation (FIG. 3) by grasping the handle and pushing down on flat area36a of lever 36.

Referring to FIG. 5c, as lever 36 is depressed in the direction of arrowA, first rod 56 will be inserted into mechanism 52 causing correspondingmovement of second rod 58 in the direction of arrow A. Movement ofsecond rod 58 in turn causes deflection of flex bar 50 and further,deflection of parallel cantilevered beams 49a and 49b. This in turncauses engagement of cleaving element 48 with fiber 14 to score or nickthe fiber at a location adjacent front face 22a of ferrule 22. Continueddepression of lever 36 will cause continued inward movement of first rod56 at which point second rod 58 will retract so that cleaving element 48will return to its original position shown in FIG. 5d, after scoringfiber 14. As above mentioned, the scoring of fiber 14 by scoring element48 is performed in a manner similar to that shown and described in theabove mentioned '744 patent.

As plunger type mechanism 52 causes retraction of second rod 58 aftercleaving of fiber 14, continuous depression of lever 36 will cause nofurther movement of cleaving element assembly 46. Thus, while operablein one continuous motion of lever 36, the scoring of fiber 14 and theactuation of pulling means 70 is accomplished in successivenon-interdependent steps. Accordingly, the operation of pulling means 70may be described with references to FIGS. 6a through 7c.

C. BREAKING OF SCORED FIBER 14

Referring to FIG. 6a, a distal end portion 14c of fiber 14 is shownextending between fiber pulling element 72 and 74 of fiber breakingmeans 70. The position illustrated in FIG. 6a is similar to that shownin FIG. 5a prior to scoring of fiber 14. In this position the distalportion 14c of fiber 14 is positioned closely adjacent to engagement pad73 of stationary puller 72. It is contemplated that with certainvariations in fiber diameter and tool compensation, the distal portion14c of fiber 14 may be either spaced closely to engagement pad 73 ofstationary puller 72 or may lie against and in engagement withengagement pad 73.

Referring to FIG. 6b, fiber breaking means 70 is shown as it ispositioned during fiber scoring (FIG. 5c). Moveable fiber pullingelement 74 is moved during fiber scoring, toward stationary element 72and into close proximaty with fiber 14 under the influence of themovement of lever 36 (not shown). As the fiber is scored, engagement pad73b of moveable puller 74 does not engage fiber 14, thus in preferredembodiment, the distal extent 14c of fiber 14 is unsupported at the timeof scoring of the fiber 14. As plunger mechanism 52 provides for theretraction of second rod 58 (FIGS. 5c and 5d) further depression oflever 36 will cause movement of only moveable puller 74.

Referring to FIG. 6c, upon further depression of lever 36 moveablepuller 74 moves into engagement with fiber 14. Engagement pad 73b ofmoveable puller 74 contacts fiber 14. Fiber 14 is then urged againstengagement pad 73a of stationary puller 72. Thus, the distal extent 14cof fiber 14 is moved substantially parallel to and out of the plane ofthe original fiber axis 14a. This movement creates a slight tensionabout the scored location, but this movement causes insufficient tensionto break the fiber at the scored location. As shown in FIG. 6c,engagement pads 73a and 73b are clamped against fiber 14 to securetherebetween a central fiber location 14b. Prior to further movement oflever 36 fiber location 14b will lie a distance S₁ from housing wall 37and also lie substantially along axis 14a.

Referring to FIG. 6d, the effects of further movement of moveable fiberpulling element 74 is shown. As fiber pulling element 74 is movedfurther in the direction of arrow A, compound movement of bothstationary fiber pulling element 72 and moveable fiber pulling element74 are achieved.

Referring to stationary fiber pulling element 72, movement of moveablefiber pulling element 74 causes deflection of cantilevered extent 72b ina direction having components both in the vertical and horizontaldirection as shown in FIG. 6d. Similarly, the deflection of thecantilevered extent 74b of moveable pulling element 74 also hasidentical movement in both the vertical and horizontal direction. Thus,engagement pads 73a and 73b will move upwardly as shown in FIG. 6d underthe influence of the movement of moveable pulling element 74 and willalso move outwardly away from housing wall 37 due to the spring movementof cantilevered spring extent 72b and 74b. Thus, engagement pads 73a and73b and accordingly, location 14b of fiber 14 secured therebetween, willmove in both a horizontal and vertical direction. The amount of fibermovement in the vertical direction (off of axis 14c) will be a distacne"d". Movement of fiber location 14b in the horizontal direction will befrom its original distance S₁ from wall 37 to a distance S₂ from wall37.

It can be seen that fiber location 14b will be displaced vertically adistance "d" from its original location and be displaced horizontally adistance S₂ minus S₁. Thus, the overall movement exhibited by theclamping pads and the fiber location 14b secured therebetween will be inthe direction somewhere between the vertical and horizontal. The vectorrepresentation of such movement is shown in FIG. 7 where actual movementof location 14d is the resultant "r" of horizontal vector S₂ minus S₁and vertical vector "d". This compound movement caused by movement ofboth stationary fiber pulling element 72 and moveable fiber pullingelement 74 causes a simultaneous bending of the fiber about the scoredlocation and axially pulling of the fiber away from the scored location.When the tension created by such movement exceeds the resistance of thefiber, the fiber will break at the scored location leaving a nearlyperpendicular end face. Once past this point of breaking the lever 36can be released and the cut end of the fiber will fall from tool 30. Inorder to prevent partial depression of trigger 36, thereby causinginsufficient bending and pulling to severe the fiber, tool 30 isequipped with a commercially available full stroke compelling mechanismwhich prevents release of the trigger prior to full cycling of the tool.A mechanism of such description is manufactured and sold for varioustools, by the assignee of the present invention, under the registeredtrademark SHURE-STAKE.

Various changes to the foregoing described and shown structures wouldnow be evident to those skilled in the art. Accordingly, theparticularly disclosed scope of the invention is set forth in thefollowing claims.

We claim:
 1. An apparatus for cleaving an elongate optical fiber retained in and extending from a ferrule, said apparatus comprising:a housing for fixedly supporting said ferrule; actuatable cleaving means movably supported on said housing adjacent said ferrule for scoring said fiber at a location on said fiber; actuatable fiber breaking means including a first spring biased pulling element fixedly supported in said housing for supporting said fiber at a second fiber location distally spaced from said first location and a second spring biased pulling element movably supported in said housing for movement into engagement with said first pulling element for grasping said fiber at said second location and for moving said fiber simultaneously in directions both transversely of said linear fiber axis and axially away from said scoring location whereby said fiber is severed at said scoring location.
 2. An apparatus in accordance with claim 1 further including actuation means for actuating said fiber cleaving means to score said fiber and for subsequently actuating said fiber breaking means to break said fiber at said scoring location.
 3. An apparatus in accordance with claim 2 wherein said actuatable cleaving means includes an elongate support member engagable with said ferrule for abutting alignment therewith, and a fiber cleaving element movably supported over said support member being movable toward said support member upon actuation of said cleaving means to score said fiber.
 4. An apparatus in accordance with claim 3 wherein said housing includes a ferrule holding member thereon for supporting said ferrule in abutting relationship with said support member.
 5. An apparatus in accordance with claim 4 wherein said fiber breaking means includes a pulling element for grasping said fiber at said second location.
 6. An apparatus in accordance with claim 5 wherein said actuation means includes a manually operable, progressively movable lever in operable engagement with said fiber cleaving element and said fiber pulling element for urging said cleaving element into contact with said fiber and subsequently activating said pulling element to pull said fiber at said second location.
 7. An apparatus in accordance with claim 2 wherein said actuation means includes single operable means for actuating both said cleaving means and said breaking means.
 8. An apparatus in accordance with claim 1 wherein each of said spring pulling elements are independently deflectably movable, movement of said pulling elements having a component in a first direction perpendicular to said fiber axis and a component in a second direction parallel to said fiber axis.
 9. An apparatus in accordance with claim 8 wherein said fiber pads are jointly movable, upon engagement of said first puller with said second puller, in a direction oblique to said first and second directions.
 10. A method of cleaving an elongate optical fiber supported in an optical fiber ferrule comprising the steps of:holding said fiber along a pre-determined axis; scoring said fiber at a first location; clamping said fiber at a second location spaced from said first location between a pair of spring biased pulling elements; and moving said pair of pulling elements against the spring bias to simultaneously axially offset said second location and pull said second location longitudinally away from said scored fiber location.
 11. A method in accordance with claim 10 wherein said scoring step includes moving a scoring element into contact with said fiber at said first location. 